1. Field
The following description relates to a technique for estimating a battery's state of charge (SOC).
2. Description of Related Art
To stably and maximally use a battery's capacity, it is important to accurately estimate the battery's present SOC.
An Ah method or a coulomb counting method is a method that estimates the SOC of a battery by deriving a used capacity from a relationship between a use current and a time, and thus the SOC is estimated based on that information. A voltage measurement method is a method that estimates a battery's charge state from a relationship between the SOC and an open circuit voltage (OCV) previously measured from the OCV of the battery. A resistance measurement method is a method that estimates the battery state from a relationship between the SOC and internal resistance of the battery.
However, the coulomb counting method and the resistance measurement method may not reflect an electrochemical characteristic of the battery that is changed into a stabilized state after termination of an operation of the battery. In the voltage measurement method, since only an external voltage is measured without information about an internal state of the battery, an estimation error may possibly occur according to the actual internal state of the battery.